Stable dispersions of poly(ethylene glycol) methyl ether-magnetite complexes in water

Abstract

We herein describe a facile synthesis of superparamagnetic magnetite ferrofluids having long-term stability in aqueous dispersions. A single-step thermal decomposition reaction of iron (III) acetylacetonate (Fe(acac)3) was carried out in the presence of poly(ethylene glycol) methyl ether (mPEG) to serve both as a reducing agent and reaction solvent. The role of number average molecular weight (Mn) of mPEG (350 and 750 g/mol) on the size and properties of the particles was investigated. Fourier-transform infrared spectrophotometry (FTIR) indicated the presence of mPEG in the polymer-magnetite complexes. According to thermogravimetric analysis (TGA), the complexes consisted of 40-66% Fe3O4, depending on the molecular weights of mPEG used. According to the transmission electron micrographs (TEM), the particles prepared in 350 g/mol mPEG exhibited the average diameter of 7.8±1.4 nm, while those in 750 g/mol mPEG were 5.3±1.1 nm. From photocorrelation spectroscopy (PCS) experiments, the size of 350 g/mol mPEG-magnetite complex and 750 g/mol mPEG-magnetite complex were 37.1±1.0nm and 35.1±0.4 nm, respectively. According to the calculation by the Debye-Scherrer equation, the sizes of 350 g/mol mPEG-magnetite complex and 750 g/mol mPEG-magnetite complex were 7.7 and 6.6 nm, respectively. They were highly crystalline and exhibited superparamagnetic properties. They were stable in aqueous dispersions with insignificant aggregation after 6 weeks of preparing. These stable, non-toxic dispersions might be potentially used in magnetically targeted biomedical applications. © 2011 Taylor & Francis.